"The significance of this concept lies in the fact that the massive installed base of
parking lots and roadways creates a low-cost solar collector an order of magnitude more productive than traditional solar cells. The significantly high surface area can offset the expected lower efficiency (compared to traditional solar cells) by several orders of magnitude, and hence result in significantly lower cost per unit of power produced," according to the paper.

Blacktops can continue to generate energy after the sun goes down, and upgrades with heat exchangers could be fit into road constructions, which are done every 10 to 12 years, Rajib Mallick, associate professor of civil and environmental engineering at Worcester Polytechnic Institute, said in a statement.

Also, wicking heat away from roads could reduce the "heat island" effect in densely populated areas where temperatures rise when buildings and pavement release heat accumulated during the day.

The researchers used computer modeling and small-scale prototypes to test alternatives to pipes for transferring asphalt heat to water.

It found that the depth of the heat exchanger was critical and that a material with higher heat conductivity, such as quartzite, can be added to asphalt to improve heat transfer.

"Our preliminary results provide a promising proof of concept for what could be a very important future source of renewable, pollution-free energy for our nation. And it has been there all along, right under our feet," Mallick said.